1. Field of the Invention
The present invention relates to a surface inspection tool and a surface inspection method, both of which are used for inspection of a wafer with patterns.
2. Description of the Related Art
In recent years, design rule shrinkage in leading edge semiconductor devices (apparatuses) has been pursued to the maximum, and not only the design rule shrinkage of pattern line widths but also thin film realization of produced films has been performed. In the case of a gate oxide film, a thin film having a film thickness of 1 to 2 nm is used and the film thickness comes close to the magnitude of irregularities (surface roughness) of a film surface. Therefore, the ratio of variation film thickness which locally varies depending on the surface roughness to the film thickness increases; and therefore, the surface roughness of the film surface which has not been brought problem in the conventional semiconductor devices is starting to have a large influence on the characteristics in the leading edge semiconductor devices.
Furthermore, configurations of wafer processing apparatuses used for manufacturing semiconductor devices have also been changed. For example, in a gate oxide film formation process, conventionally, there is a general mode in which several tens to about one hundred of wafers are processed in block by using a vertical type oxidation diffusion apparatus. However, nowadays, the use of an oxidation diffusion apparatus of sheet process suitable for large diameter realization of wafers has been rapidly spread; and consequently, variations in film thickness and surface roughness between the wafers due to the sheet process becomes one factor of degradation in yield of the semiconductor devices.
Therefore, in the production process of the leading edge semiconductor devices, it is necessary to set production conditions which does not easily cause variations in the film thickness and surface roughness of the produced films, and to strictly control the film thickness and surface roughness of the produced films manufactured under the production conditions.
As technology for measuring the surface roughness of the conventional wafer, there are proposed the following methods: (1) a method in which a wafer is cut or processed by focused ion beam (FIB) process and the cut surface is observed with an electron microscope; (2) a method in which surface roughness of a wafer is measured with an atomic force microscope (AFM); (3) a method in which laser light is made incident on a wafer surface and scattering light caused by the surface roughness from the wafer surface is received to measure the surface roughness of the wafer, as disclosed in Japanese Patent Application Laid open (JP-A) No. 2006-64496A1 and JP-A No. 2002-340537A1. Furthermore, in JP-A No. 7-19844A1, there is proposed a method in which an X-ray is used in place of laser light.